Wilson disease

Synonyms

4

Overview

Wilson disease is an inherited disorder in which excessive amounts of copper accumulate in the body, particularly in the liver, brain, and eyes. The signs and symptoms of Wilson disease usually first appear between the ages of 6 and 45, but they most often begin during the teenage years. The features of this condition include a combination of liver disease and neurological and psychiatric problems.

Copper plays a key role in the development of healthy nerves, bones, collagen and the skin pigment melanin. Normally, copper is absorbed from your food, and any excess is excreted through bile — a substance produced in your liver.

But in people with Wilson's disease, copper isn't eliminated properly and instead accumulates, possibly to a life-threatening level. When diagnosed early, Wilson's disease is treatable, and many people with the disorder live normal lives.

Liver disease is typically the initial feature of Wilson disease in affected children and young adults; individuals diagnosed at an older age usually do not have symptoms of liver problems, although they may have very mild liver disease. The signs and symptoms of liver disease include yellowing of the skin or whites of the eyes (jaundice), fatigue, loss of appetite, and abdominal swelling.

Nervous system or psychiatric problems are often the initial features in individuals diagnosed in adulthood and commonly occur in young adults with Wilson disease. Signs and symptoms of these problems can include clumsiness, tremors, difficulty walking, speech problems, impaired thinking ability, depression, anxiety, and mood swings.

In many individuals with Wilson disease, copper deposits in the front surface of the eye (the cornea) form a green-to-brownish ring, called the Kayser-Fleischer ring, that surrounds the colored part of the eye. Abnormalities in eye movements, such as a restricted ability to gaze upwards, may also occur.

Symptoms

The main sites of copper accumulation are the liver and the brain, and consequently liver disease and neuropsychiatric symptoms are the main features that lead to diagnosis. People with liver problems tend to come to medical attention earlier, generally as children or teenagers, than those with neurological and psychiatric symptoms, who tend to be in their twenties or older. Some are identified only because relatives have been diagnosed with Wilson's disease; many of these, when tested, turn out to have been experiencing symptoms of the condition but have not received a diagnosis.

  • Liver disease:   

Liver disease may present itself as tiredness, increased bleeding tendency or confusion (due to hepatic encephalopathy) and portal hypertension. The latter, a condition in which the pressure in the portal vein is markedly increased, leads to esophageal varices, blood vessels in the esophagus that may bleed in a life-threatening fashion, as well as enlargement of the spleen (splenomegaly) and accumulation of fluid in the abdominal cavity (ascites). On examination, signs of chronic liver disease such as spider angiomata (small distended blood vessels, usually on the chest) may be observed. Chronic active hepatitis has caused cirrhosis of the liver in most by the time they develop symptoms. While most people with cirrhosis have an increased risk of hepatocellular carcinoma (liver cancer), this risk is relatively very low in Wilson's disease.

About 5% of all people are diagnosed only when they develop fulminant acute liver failure, often in the context of a hemolytic anemia (anemia due to the destruction of red blood cells). This leads to abnormalities in protein production (identified by deranged coagulation) and metabolism by the liver. The deranged protein metabolism leads to the accumulation of waste products such as ammonia in the bloodstream. When these irritate the brain, the person develops hepatic encephalopathy (confusion, coma, seizures and finally life-threatening swelling of the brain).

  • Neuropsychiatric symptoms:  

About half the people with Wilson's disease have neurological or psychiatric symptoms. Most initially have mild cognitive deterioration and clumsiness, as well as changes in behavior. Specific neurological symptoms usually then follow, often in the form of parkinsonism (cogwheel rigidity, bradykinesia or slowed movements and a lack of balance are the most common parkinsonian features) with or without a typical hand tremor, masked facial expressions, slurred speech, ataxia (lack of coordination) or dystonia (twisting and repetitive movements of part of the body). Seizures and migraine appear to be more common in Wilson's disease. A characteristic tremor described as "wing-beating tremor" is encountered in many people with Wilson's; this is absent at rest but can be provoked by extending the arms.

Cognition can also be affected in Wilson's disease. This comes in two, not mutually exclusive, categories: frontal lobe disorder (may present as impulsivity, impaired judgement, promiscuity, apathy and executive dysfunction with poor planning and decision making) and subcortical dementia (may present as slow thinking, memory loss and executive dysfunction, without signs of aphasia, apraxia or agnosia). It is suggested that these cognitive involvements are related and closely linked to psychiatric manifestations of the disease.

Psychiatric problems due to Wilson's disease may include behavioral changes, depression, anxiety and psychosis. Psychiatric symptoms are commonly seen in conjunction with neurological symptoms and are rarely manifested on their own. These symptoms are often poorly defined and can sometimes be attributed to other causes. Because of this, diagnosis of Wilson's disease is rarely made when only psychiatric symptoms are present.

Medical conditions have been linked with copper accumulation in Wilson's disease:

  • Eyes: Kayser–Fleischer rings (KF rings), a pathognomonic sign, may be visible in the cornea of the eyes, either directly or on slit lamp examination as deposits of copper in a ring around the cornea. They are due to copper deposition in Descemet's membrane. They do not occur in all people with Wilson's disease. Wilson's disease is also associated with sunflower cataracts exhibited by brown or green pigmentation of the anterior and posterior lens capsule. Neither cause significant visual loss. KF rings occur in approximately 66% of diagnosed cases (more often in those with neurological symptoms rather than with liver problems).
  • Kidneys: renal tubular acidosis, a disorder of bicarbonate handling by the proximal tubules leads to nephrocalcinosis (calcium accumulation in the kidneys), a weakening of bones (due to calcium and phosphate loss), and occasionally aminoaciduria (loss of essential amino acids needed for protein synthesis).
  • Heart: cardiomyopathy (weakness of the heart muscle) is a rare but recognized problem in Wilson's disease; it may lead to heart failure (fluid accumulation due to decreased pump function) and cardiac arrhythmias (episodes of irregular and/or abnormally fast or slow heart beat).
  • Hormones: hypoparathyroidism (failure of the parathyroid glands leading to low calcium levels), infertility, and habitual abortion

Other signs and symptoms may include:

  • Menstrual period irregularities, increased risk of miscarriage and infertility in women
  • Anemia
  • Easy bruising and prolonged bleeding
  • Kidney stones
  • Early-onset arthritis
  • Osteoporosis
  • Fatigue, lack of appetite or abdominal pain
  • Jaundice, a yellowing of the skin and the whites of the eye
  • A tendency to bruise easily
  • Fluid buildup in the legs or abdomen
  • Problems with speech, swallowing or physical coordination
  • Uncontrolled movements or muscle stiffness

Causes

Wilson disease is caused by a buildup of copper in the body. Normally, copper from the diet is filtered out by the liver and released into bile, which flows out of the body through the gastrointestinal tract. People who have Wilson disease cannot release copper from the liver at a normal rate, due to a mutation of the ATP7B gene. When the copper storage capacity of the liver is exceeded, copper is released into the bloodstream and travels to other organs—including the brain, kidneys, and eyes.

The gene ATP7B encodes a protein that plays an important role in the transport of copper from the liver to the rest of the body. It also helps remove excess copper from the body. Mutations in the ATP7B gene prevent this protein from working properly, which can lead to an accumulation of copper in the body. Because high levels of copper are toxic, this buildup can damage tissues and organs and cause the many signs and symptoms of Wilson disease.

Wilson's disease is inherited as an autosomal recessive trait, which means that to develop the disease you must inherit two copies of the defective gene, one from each parent. If you receive only one abnormal gene, you won't become ill yourself, but you're considered a carrier and can pass the gene to your children.

Prevention

People with a familial history of Wilson disease, should have a genetic consulting.

Diagnosis

Wilson disease may be suspected on the basis of any of the symptoms mentioned above, or when a close relative has been found to have Wilson's. Most have slightly abnormal liver function tests such as a raised aspartate transaminase, alanine transaminase and bilirubin level. If the liver damage is significant, albumin may be decreased due to an inability of damaged liver cells to produce this protein; likewise, the prothrombin time (a test of coagulation) may be prolonged as the liver is unable to produce proteins known as clotting factors. Alkaline phosphatase levels are relatively low in those with Wilson's-related acute liver failure. If there are neurological symptoms, magnetic resonance imaging (MRI) of the brain is usually performed; this shows hyperintensities in the part of the brain called the basal ganglia in the T2 setting. MRI may also demonstrate the characteristic "face of the giant panda" pattern.

There is no totally reliable test for Wilson's disease, but levels of ceruloplasmin and copper in the blood, as well of the amount of copper excreted in urine during a 24-hour period, are together used to form an impression of the amount of copper in the body. The gold standard or most ideal test is a liver biopsy.

  • Ceruloplasmin:  

Levels of ceruloplasmin are abnormally low (<0.2 g/L) in 80–95% of cases. It can, however, be present at normal levels in people with ongoing inflammation as it is an acute phase protein. Low ceruloplasmin is also found in Menkes disease and aceruloplasminemia, which are related to, but much rarer than Wilson's disease.

The combination of neurological symptoms, Kayser–Fleisher rings and a low ceruloplasmin level is considered sufficient for the diagnosis of Wilson's disease. In many cases, however, further tests are needed.

  • Serum and urine copper:  

Serum copper is paradoxically low but urine copper is elevated in Wilson's disease. Urine is collected for 24 hours in a bottle with a copper-free liner. Levels above 100 μg/24h (1.6 μmol/24h) confirm Wilson's disease, and levels above 40 μg/24h (0.6 μmol/24h) are strongly indicative. High urine copper levels are not unique to Wilson's disease; they are sometimes observed in autoimmune hepatitis and in cholestasis (any disease obstructing the flow of bile from the liver to the small bowel).

In children, the penicillamine test may be used. A 500 mg oral dose of penicillamine is administered, and urine collected for 24 hours. If this contains more than 1600 μg (25 μmol), it is a reliable indicator of Wilson's disease. This test has not been validated in adults.

  • Liver biopsy:  

Once other investigations have indicated Wilson disease, the ideal test is the removal of a small amount of liver tissue through a liver biopsy. This is assessed microscopically for the degree of steatosis and cirrhosis, and histochemistry and quantification of copper are used to measure the severity of the copper accumulation. A level of 250 μg of copper per gram of dried liver tissue confirms Wilson's disease. Occasionally, lower levels of copper are found; in that case, the combination of the biopsy findings with all other tests could still lead to a formal diagnosis of Wilson's.

In the earlier stages of the disease, the biopsy typically shows steatosis (deposition of fatty material), increased glycogen in the nucleus, and areas of necrosis (cell death). In more advanced disease, the changes observed are quite similar to those seen in autoimmune hepatitis, such as infiltration by inflammatory cells, piecemeal necrosis and fibrosis (scar tissue). In advanced disease, finally, cirrhosis is the main finding. In acute liver failure, degeneration of the liver cells and collapse of the liver tissue architecture is seen, typically on a background of cirrhotic changes. Histochemical methods for detecting copper are inconsistent and unreliable, and taken alone are regarded as insufficient to establish a diagnosis.

  • Genetic testing:     

Mutation analysis of the ATP7B gene, as well as other genes linked to copper accumulation in the liver, may be performed. Once a mutation is confirmed, it is possible to screen family members for the disease as part of clinical genetics family counseling.

Prognosis

The long-term outlook (prognosis) for people with Wilson disease varies and largely depends on timely diagnosis and treatment. If the condition is detected early and treated appropriately, people with Wilson disease can usually enjoy normal health and a normal lifespan. Unfortunately, untreated Wilson disease is associated with severe brain damage, liver failure, and death. Liver and neurologic damage that occurs prior to treatment may improve, but it is often permanent.

Treatment

There is currently no cure for Wilson disease; however, therapies exist that aim to reduce or control the amount of copper that accumulates in the body. Affected people require lifelong treatment, which may include certain medications and/or dietary modifications. If treatment is not effective or if liver failure develops, a liver transplant may be necessary.

Dietary:  

In general, a diet low in copper-containing foods is recommended with the avoidance of mushrooms, nuts, chocolate, dried fruit, liver, and shellfish.

Medication:   

Medical treatments are available for Wilson's disease. Some increase the removal of copper from the body, while others prevent the absorption of copper from the diet.

Generally, penicillamine is the first treatment used. This binds copper (chelation) and leads to excretion of copper in the urine. Hence, monitoring of the amount of copper in the urine can be done to ensure a sufficiently high dose is taken. Penicillamine is not without problems: about 20% experience a side effect or complication of penicillamine treatment, such as drug-induced lupus (causing joint pains and a skin rash) or myasthenia (a nerve condition leading to muscle weakness). In those who presented with neurological symptoms, almost half experience a paradoxical worsening in their symptoms. While this phenomenon is observed in other treatments for Wilson's, it is usually taken as an indication for discontinuing penicillamine and commencing second-line treatment. Those intolerant to penicillamine may instead be commenced on trientine hydrochloride, which also has chelating properties. Some recommend trientine as first-line treatment, but experience with penicillamine is more extensive. A further agent, under clinical investigation by Wilson Therapeutics, with known activity in Wilson's disease is tetrathiomolybdate. This is regarded as experimental, though some studies have shown a beneficial effect.

Once all results have returned to normal, zinc (usually in the form of a zinc acetate prescription called Galzin) may be used instead of chelators to maintain stable copper levels in the body. Zinc stimulates metallothionein, a protein in gut cells that binds copper and prevents their absorption and transport to the liver. Zinc therapy is continued unless symptoms recur or if the urinary excretion of copper increases.

Trientine HCl (Brand name: Syprine ) is a FDA-approved indication: Treatment of patients with Wilson's disease who are intolerant, or inadequately responsive to penicillamine. 

In rare cases where none of the oral treatments are effective, especially in severe neurological disease, dimercaprol (British anti-Lewisite) is occasionally necessary. This treatment is injected intramuscularly (into a muscle) every few weeks and has unpleasant side effects such as pain.

People who are asymptomatic (for instance, those diagnosed through family screening or only as a result of abnormal test results) are generally treated, as the copper accumulation may cause long-term damage in the future. It is unclear whether these people are best treated with penicillamine or zinc acetate.

Physical therapy:  

Physiotherapy is beneficial for patients with the neurologic form of the disease. The copper chelating treatment may take up to six months to start working, and physical therapy can assist in coping with ataxia, dystonia, and tremors, as well as preventing the development of contractures that can result from dystonia.

Transplantation:

Liver transplantation is an effective cure for Wilson's disease but is used only in particular scenarios because of the risks and complications associated with the procedure. It is used mainly in people with fulminant liver failure who fail to respond to medical treatment or in those with advanced chronic liver disease. Liver transplantation is avoided in severe neuropsychiatric illness, in which its benefit has not been demonstrated.

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